1. Field of the Invention
The present invention relates to a continuous conveying type bag filling and packaging machine that moves multiple grippers along a racetrack-shaped annular path at a constant speed and, in the process of movement of grippers, carries out packaging operations, such as supplying of a bag to the grippers and holding of the bag at two edges with the grippers, opening of the mouth of the bag, filling of the bag with material to be packaged, sealing of the mouth of the bag, and the like.
2. Description of the Related Art
U.S. Pat. No. 4,509,313 discloses a continuous conveying type bag filling and packaging machine, and this bag filling and packaging machine includes multiple groups of grippers disposed at regular intervals and traveling at a constant speed along a racetrack-shaped annular path, a bag supplying apparatus disposed along the annular path, a bag mouth opening apparatus, a filling apparatus, a sealing apparatus, and the like. In this continuous conveying type bag filling and packaging machine, the filling apparatus is provided with a plurality of elevating hoppers, which are disposed above an arcuate (semi-circular) portion on one side of the annular path at regular intervals (regular angular intervals) along a circular path that is concentric with the arcuate portion, and these hopper continuously rotate in synchronism with the grippers. As the grippers travel along the arcuate portion on one side of the annular path, the bags held by the grippers are filled with the material to be packaged through the elevating (rising and lowering) hoppers.
As the grippers continuously travel (rotate) along the arcuate portion on one side of the annular path, the elevating hoppers continuously rotate in synchronism with the grippers. During this continuous rotation, the elevating hopper is lowered from a position directly above a bag held by the grippers (a standby position) to a filling position, and a lower end opening of the hopper is inserted into the mouth of the bag, and then the material to be packaged is deposited into the elevating hopper, falling into the bag through the lower end opening; after this, the hopper is raised, the lower end opening is retracted out of the mouth of the bag, and then the elevating hopper returns to the standby position.
A similar continuous conveying type bag filling and packaging machine is disclosed in Japanese Patent Application Laid-Open (Kokai) No. 2009-161230. In this continuous conveying type bag filling and packaging machine, a continuously rotating guide member, which is raised and lowered in conjunction with the elevating hoppers and continuously rotates, is provided at a position below each elevating hopper. The guide member has a pair of opposed frames that are opened and closed by an air cylinder or other drive means. When the frames are closed, the lower portion of the guide member becomes narrower, and the lower end can be inserted into the mouth of a bag; while, on the other hand, when the frames are opened, the lower end of the guide member is released (opened), and the material to be packaged falls downwardly and fills up the bag.
In the continuous conveying type bag filling and packaging machines described above, a predetermined amount of material to be packaged is supplied to the elevating hoppers for each rotation; and in the synchronized zone (which is a zone wherein the grippers and elevating hoppers rotate in synchronism), the bags held by the grippers are filled with the material to be packaged through the elevating hoppers (or through elevating hoppers and guide members). In certain cases, however, the weight of the material to be packaged that is supplied to an elevating hopper may be either insufficient or excessive.
If the weight of the material to be packaged that is supplied to an elevating hopper is insufficient, the resultant non-compliant bag (which has insufficient filling weight) is removed from the production line during the subsequent steps. However, if the weight of the material to be packaged is excessive, this would cause that the material to be packaged deposited in the bag gets into the seal portion of the bag mouth, spills from the bag mouth, and so on. As a result, later, this may adversely affect subsequent production by operational faults in the sealing apparatus, contamination of the bag filling and packaging machine and the production line during the subsequent steps, and so on.